Cellulose dispersion

Abstract

A cellulose dispersion which is a dispersion comprising a dispersing medium and a cellulose having a fraction of cellulose I type crystal component of not more than 0.1 and a fraction of cellulose II type crystal component of not more than 0.4 and in which the average particle diameter of the constitutive cellulose is not more than 5 μm. A cellulose particulate and a cellulose composite particulate which have an average particle diameter of 0.2 to 20 μm, a ratio of long diameter (L) to short diameter (D) observed through a scanning electron microscope (L/D) of not more than 1.2 and a coefficient of aggregation of 1.0 to 3.0. The present invention provides a cellulose dispersion which has an excellent effect such as dispersion stability or the like and is high in transparency. Moreover, it provides a cellulose particulate and a cellulose composite particulate which have such performances as no rough feel, excellent rolling properties, high dispersibility and the like.

What is claimed is:  
     
       1. A cellulose dispersion which is a dispersion comprising a dispersing medium and a cellulose having crystal forms of cellulose I and cellulose II, wherein a crystallinity of cellulose I is not more than 0.1 and a crystallinity of cellulose II is not more than 0.4 and wherein the average particle diameter of the cellulose in the dispersion is not more than 5 μm. 
     
     
       2. The cellulose dispersion according to  claim 1 , wherein the average degree of polymerization (DP) is not more than 100 and when the cellulose concentration of the cellulose dispersion is adjusted to 0.05% by weight, the transmittance of the dispersion to a visible light of a wavelength of 660 nm is not less than 40%. 
     
     
       3. The cellulose dispersion according to  claim 2 , wherein the average particle diameter of the cellulose is not more than 2 μm. 
     
     
       4. The cellulose dispersion according to  claim 1 , wherein when the cellulose concentration is adjusted to 0.05% by weight, the transmittance of the dispersion to a visible light of a wavelength of 660 nm is not less than 80%. 
     
     
       5. The cellulose dispersion according to  claim 2 , wherein when the cellulose concentration is adjusted to 0.05% by weight, the transmittance of the dispersion to a visible light of a wavelength of 660 nm is not less than 80%. 
     
     
       6. The cellulose dispersion according to  claim 2 ,  4  or  5 , wherein the dispersing medium is water and/or an organic solvent. 
     
     
       7. The cellulose dispersion according to  claim 5 , wherein the organic solvent is a water-soluble alcohol. 
     
     
       8. A composite cellulose dispersion which comprises the cellulose dispersion according to  claim 1 ,  2 ,  4  or  5  and a functional additive compatible with the dispersing medium, wherein when the cellulose concentration in the composite cellulose dispersion is adjusted to 0.05% by weight, the transmittance of the dispersion to a visible light of a wavelength of 660 nm is not less than 40%. 
     
     
       9. The composite cellulose dispersion according to  claim 8 , wherein the transmittance is not less than 80%. 
     
     
       10. The composite cellulose dispersion according to  claim 8 , wherein the functional additive is selected from the group consisting of a polyhydric alcohol, a water-soluble polysaccharide, a water-soluble polymer and a water-soluble perfume. 
     
     
       11. A process for producing a cellulose dispersion, which comprises dissolving a cellulose in an aqueous inorganic acid solution to prepare a cellulose solution, reprecipitating the cellulose solution in water or a coagulating agent containing not less than 50% by weight of water to prepare a cellulose suspension, subjecting the cellulose in the suspension to acid hydrolysis treatment, and subsequently removing the acid from the suspension. 
     
     
       12. A process for producing a cellulose dispersion, which comprises dissolving a cellulose in an aqueous inorganic acid solution to prepare a cellulose solution, reprecipitating the cellulose solution in water or a coagulating agent containing not less than 50% by weight of water to prepare a cellulose suspension, subsequently preparing a dehydrated cake of the cellulose from the suspension, thereafter introducing the dehydrated cake into water at not less than 50° C. to subject the cellulose to acid hydrolysis treatment and then removing the acid from the suspension. 
     
     
       13. The process for producing a cellulose dispersion according to  claim 11 , which comprises, after the step of removing the acid from the suspension, further subjecting the suspension to high-power grinding treatment. 
     
     
       14. The process for producing a cellulose dispersion according to  claim 12 , which comprises, after the step of removing the acid from the suspension, further subjecting the suspension to high-power grinding treatment. 
     
     
       15. The process for producing a cellulose dispersion according to  claim 11 ,  12 ,  13  or  14 , wherein the inorganic acid is sulfuric acid. 
     
     
       16. The process for producing a cellulose dispersion according to  claim 11 ,  12 ,  13  or  14 , wherein the removal of the acid from the suspension is effected by adjusting the pH of the suspension to not less than 2. 
     
     
       17. The process for producing a cellulose dispersion according to  claim 11 ,  12 ,  13  or  14 , wherein the water in the cellulose dispersion obtained by removing the acid is replaced with a water-soluble organic solvent. 
     
     
       18. The process for producing a cellulose dispersion according to  claim 11 ,  12 ,  13  or  14 , wherein a functional additive is added to the cellulose dispersion obtained by removing the acid. 
     
     
       19. The process for producing a composite cellulose dispersion according to  claim 18 , wherein after the step of adding the above functional additive, the dispersion is further subjected to high-power grinding treatment. 
     
     
       20. A cellulose particulate which is composed of a cellulose having crystal forms of cellulose I and cellulose II, wherein a crystallinity of cellulose I is not more than 0.1 and a crystallinity of cellulose II is not more than 0.4, and which has an average particle diameter of 0.2 to 20 μm, a ratio of long diameter (L) to short diameter (D) as observed through a scanning electron microscope (L/D) of not more than 1.2 and a coefficient of aggregation of 1.0 to 3.0, provided that the coefficient of aggregation=(average particle diameter calculated from the volume reduced distribution obtained by a laser diffraction-scattering type particle size distribution measuring apparatus)/(average particle diameter of volume reduction by a scanning electron microscope). 
     
     
       21. The cellulose particulate according to  claim 20 , wherein the average degree of polymerization (DP) is not more than 100 and the L/D value after pressing at a pressure of 100 kgf/cm 2  is not more than 1.2. 
     
     
       22. A cellulose composite particulate which is a particulate in which at least one functional additive is dispersed in the cellulose particulate according to  claim 20  or  21  and which particulate has an average particle diameter of 0.2 to 20 μm, a ratio of long diameter (L) to short diameter (D) as observed through a scanning electron microscope (L/D) of not more than 1.2 and a coefficient of aggregation of 1.3 to 3.0. 
     
     
       23. The cellulose composite particulate according to  claim 20 , wherein the functional additive is at least one member selected from the group consisting of an oil type compound, a water-soluble polymer, a humectant, a surface active agent, a metal oxide, an ultraviolet screener, an inorganic salt, a metal powder, a gum, a dye, a pigment, carbon black, a silica compound, a latex, an emulsion, an amino acid, a perfume and an antiseptic agent. 
     
     
       24. A process for producing a cellulose particulate, which comprises subjecting the cellulose dispersion according to  claim 1 ,  2 ,  3 ,  4  or  5  to granulation and drying by a spray drying method. 
     
     
       25. A process for producing a cellulose composite particulate, which comprises mixing the cellulose dispersion according to  claim 1 ,  2 ,  3 ,  4  or  5  with at least one functional additive and then subjecting the resulting mixed liquid to granulation and drying by a spray drying method. 
     
     
       26. A cellulose coating film obtained by coating the cellulose dispersion according to  claim 1 ,  2 ,  3 ,  4  or  5  on the surface of an inorganic material substrate, a plastic substrate or a paper and then drying the same. 
     
     
       27. A cellulose composite coating film obtained by coating the composite cellulose dispersion according to  claim 7 , on the surface of an inorganic material substrate, a plastic substrate or a paper and then drying the same. 
     
     
       28. The composite cellulose dispersion according to  claim 8 , wherein the functional additive is selected from the group consisting of a polyhydric alcohol, a water-soluble polysaccharide, a water-soluble polymer and a water-soluble perfume. 
     
     
       29. A cellulose composite coating film obtained by coating the composite cellulose dispersion according to  claim 9  on the surface of an inorganic material substrate, a plastic substrate or a paper and then drying the same.